Combustion apparatus for use with boilers



IIWENTOR GABRIEL BROLA G. BROLA COMBUSTION APPARATUS FOR USE WITH BOILERS Sept. 17, 1957 Filed Nov. 5, 1952 Mzmuuuum Sept. 17, 1957 BROLA 2,806,516

' COMBUSTIUN APPARATUS FOR USE WITH BOILERS Filed NOV. 3, 1952 2 Sheets-Sheet 2 fig. 2

Axooo 0 no 30 26. on --27b 25 v 24 I MM uuuunnm IHVENTOR GABRIEL BROLA Patented Sept. 17, 1957 CONIBUSTION APPARATUS FOR USE WITH BOILERS Gabriel Brola, Paris, France, assignor to The Society Thermo-Mecaniqne, Dordogne, France, a French com- This invention relates to combustionv apparatus particu-' larly adapted for use with boilers generating hotwater or steam. v 1

An object of the invention is to provide combustion apparatus cable of eificiently producing intensely heated products of combustion. I I

In accordance with an aspect of the invention, a combustion apparatus particularly adapted for use with a boiler generating hot water on steam comprises a main combustion chamber having inlet and outlet ends, an auxiliary combustion chamber opening into the main combustion chamber at the inlet end of the latter, a tuyere disposed substantially completely within the auxiliary combustion chamber to define an auxiliary combustion space between the tuyere and the auxiliary combustion chamber, the tuyere being convergent-divergent and having openings at the narrow portion thereof communication the interior of the tuyere with the auxiliary combustion space, the major supply of fuel and primary. air being admitted to the interior of the tuyere, while an auxiliary supply of fuel and auxiliary air are admitted to the auxiliary combustion space to burn in the latter, thereby heating the tuyere to effect heating of the mixture of fuel and air admitted to the latter and permiting burning gases from the auxiliary combustion space to pass through the openings of the tuyere and ignite the fuel and air mixture in the latter.

Further, in accordance with the present invention, a combustion apparatus of the above described character may have its auxiliary combustion chamber tapering at the end thereof opening into the main combustion chamber to project the hot products of combustion from the auxiliary combustion space laterally inward for mixing with the primary fuel and air mixture issuing from the tuyere.

Other advantages and characteristic features of the invention will become apparent in the following detailed description of two embodiments thereof given merely as non-limitative examples with reference to the accompanying drawings, in which:

Fig. 1 is a sectional view of a combustion apparatus embodying the present invention; and

Fig. 2 represent in perspective another embodiment of combustion apparatus according to the invention, and which is shown partly in section.

Referring initially to Fig. 1 of the drawings, it will be seen that a combustion apparatus for a boiler, in accordance with the present invention, comprises a cylindrical tube of refractory steel sheet 21 which is surrounded by a spaced sheath 22. The assembly of the tube 21 and sheath 22 is placed at the upper part of the central space 12 of a boiler (not shown) and is fixed to a head plate 7. The passage 23 existing between the tube 21 and sheath 22 communicates with a space above the plate 7 and also with the lower portion of the combustion chamber defined within the tube 21 through openings 24 for the admission of air. The upper portion of the combustion chamber communicates also with the space 10 by openings 25 in the tube 21 for the admission of air; These openings 24 and 25 are directed tangentially. The cylindrical combustion chamber is surmonted by an auxiliary annular combustion chamber 26 inside which is placed a convergent-divergent tuyere 27 of nickel steel,

with the chamber 26 having a concave internal surface.

At the center of the tuyere 27 is disposed the principal injector 28 which'feeds'the cylindrical chamber 21 With atomised fuel and round which is disposed a row of inclined blades 29 in order to impart a whirling motion to the air passing through the tuyere.

The annular auxiliary combustion space defined between the auxiliary combustion chamber 26 and the tuyere 27 is provided in its external wall and in its internal wall with orifices 30 and 31, respectively, for the admission of air and a plurality of fuel injectors 32 extend into the auxiliary combustion space to supply auxiliary fuel to thelatter. An ignition plug (not shown) may be provided within the auxiliary combustion space to ignite the auxiliary fuel and air admitted to the latter.

The air for supporting combustion of fuel within the above described apparatus is admitted through the space A portion of this air then enters the annular chamber -26 through theopenings 30 and 31 in which it ensures the combustion of the fuel injected at 32. The combustion theauxiliary combustion space between chamber 26 and tuyere 27 is carried out at a slow speed so that the flame remains stationary in the auxiliary combustion space for all working conditions. This flame is used primarily as a pilot flame, but it also strongly heats the metallic wall of the central tuyere and, finally, it generates combustion gases at a very high temperature.

The air and the fuel which feed the cylindrical chamber within tube 21 pass through the tuyere 27 and, as the Wall of the latter is raised to a high temperature, the intense radiation partially vaporises the atomised fuel and preheats the air. On issuing from the tuyere, the fuel and the 'air mixwith the hot gases coming from the annular auxiliary combustion space. The fuel is completely vaporised and the vaporised mixture in contact with the hot gases is raised to a temperature which is higher than its ignition point. Owing to this, any delay in the burning of the vaporised mixture is decreased and its preheated state increases the speed of the kinetic reaction of combustion, so that the flame front becomes stationary at the entrance of the cylindrical chamber 21.

Since the speed of reaction of combustion of a vaporised mixture is a function of the preheating temperature, the chamber according to the invention enables the speed of combustion to be increased at will only by increasing the output of fuel burned in the annular space between chamber 26 and tuyere 27 In this manner, the flame front can be stabilised in the main combustion chamber within the tube 21 for high gaseous conditions of flow and, consequently, the combustion intensity in the chamber can be increased.

The secondary air enters the main combustion chamber within tube 21 through the openings 24 and 25. The air which passes through the openings 24 preliminarily circulates between the tube 21 and sheath 22 to cool the tube 21 around the main combustion chamber.

Besides, as the fuel atomised by the principal injector 28 passes through the tuyere 27, the wall of which is raised to a high temperature, and as this wall is made of steel sheet loaded with nickel, the incandescent wall effect produces a catalytic action which enhances the reaction of combustion of the heavy fuels or of the pulverised coal. Further, burning gases from the auxiliary combustion space between the auxiliary chamber 26 and "tuyere 27 can enter the latter, through the openings 31,

at the narrow portion of the convergent-divergent tuyere,

thereby to ignite the fuel and air mixture in the latter.

-By this arrangement of superposed chambers with combustion in stages, the intensity of the combustion can be increased and very heavy fuels can be easily burned. This type of combustion apparatus may be used in all the industries in which it is necessary to produce hot gases and to generate a large quantity of heat ina small space. It may be used advantageously for burning powdered coal or fuel waste, provided that the preheating flame of the annular chamber is fed with good quality fuel or with a gaseous fuel.

It is well understood that the invention is not limited to the embodiment which has been just described and that the latter can be modified without departing from the scope of the invention as defined in the claims. Particularly, the auxiliary and main combustion chambers may be flat. An example of suchan arrangement is represented in Fig. 2, in which the principal or main combustion chamber 35 is of rectangular cross-section, while the-auxiliary combustion chamber is defined by two plates 26a and 26b which are concave toward each other and represent diametrically opposed sections of a cylinder :arranged with its axis perpendicular to the direction of flow of gases through the combustion apparatus. Thetuyere of the apparatus of Fig. 2 is also defined by spaced apart curved plates 27a and 27bwhich are arranged betweenthe plates 26a and 26b and have their convex sides fac ing each other so that the space between the plates 27a and 27b is convergent divergent. Thus, in the embodiment of Fig. 2, the auxiliary combustion space defined between theauxiliary combustion chamber 26a.2'6b and the tuyere 27a-2'7b is divided intotwo parts at opposite sides of the latter and having rectangular cross-sections, for relation to the rectangular cross-sections of themain combustion chamber 35. Otherwise, the embodimentof Fig. 2 is similarto the described embodiment of- Fig; l, and other parts of the embodiment of- Fig. 2 are identified on the latter by the same reference numerals used in connection with the corresponding parts on Fig. 1.

Whatis claimed is:

1'. A combustion apparatus particularly adapted for use with boilers generating 'hot water or steam; said apparatus comprising a main combustion chamber having inlet and outlet ends, an auxiliary combustion chamber opening into said main combustion chamber at said inlet end of. the latter, a. tuyere disposed substantially completely within said auxiliary combustion chamber to define an auxiliary combustion space between said tuyere and said auxiliary combustion chamber, said tuyere being 5 convergent-divergent and having openings at the narrow portion thereof to communicate the interior of said tuyere with said auxiliary combustion space, a main fuel injector in. said tuyere for admitting, the major supply of fuel to the latter, means admitting primary air to said tuyere for supporting the combustion of fuel issuing from said maininjector, and means for admitting an auxiliary supply of fuel and auxiliary air to said auxiliary combustion chamber outside of said tuyere to burn in said auxiliary combustion spaee, thereby to' heat said tuyere and effect heating of the fuel and air mixture admitted to the latter, while burning gases fromsaid' auxiliary combustion space can enter the interior of said tuyere through said openings at the narrow portion of the latter to ignite the fuel and air mixture in said tuyere.

' 2. A combustion apparatus as in claim 1; wherein 'said auxiliary combustion chamber tapers at the end thereof opening into said main combustion chamber to project. the hot products of combustion from said auxiliary combustion space laterally inward for mixing with References Cited in the file of this patent UNITED STATES PATENTS- 1,339 Dewitt Sept. 25, 1839 146,039 Allison Dec. 30, 1873 523,672 Long July 31, 1894 747,072. Human Dec. 1-5, 1903 870,821 Hall Nov. 12, 1907 1,251,084 Mitchell -Dec. 2-5, 1917' 1,788,716 Hepburn Jan. 13, 1931 2,085,256 Feldt June 29 19-37 2,308,902 Weller Jan. 19, 1943 2,443,707 Korsgren June 22, 1948 40 2,446,059 Peterson et al; July 27, 1948 2,470,860 Parish May 24, 1949' 2,592,110? 7 Berggrenet' a1. Apr. 8, 1952' 2,632,299 Loughran Mar. 24, 1953 2,635,426 Meschino Apr. 21', 1953 2,647,369 Leduc Aug. 4,- 1953 2,704,435 Allen Mar. 22, 1955 the primary fuel and air mixture issuing from said tuyere. 

